Nickel concentrations in human tissues and gallbladder bile were determined by analysis of postmortem specimens from ten consecutive autopsies of adult persons. The tissue samples were collected and homogenized with precautions to avoid nickel contamination and were analyzed by electrothermal atomic absorption spectrophotometry with Zeemann background correction. In decreasing order of mean nickel concentrations, the following results were obtained (mean and range, microgram/kg dry weight, N = 7-10): lung 173 (71-371), thyroid 141 (41-240), adrenal 132 (53-241), kidney 62 (19-171), heart 54 (10-110), liver 50 (11-102), brain 44 (20-65), spleen 37 (9-95), and pancreas 34 (7-71). In five specimens of gallbladder bile, nickel concentrations averaged 2.3 +/- 0.8 micrograms/l (range 1.5-3.3). These data furnish reference values for use in evaluating tissue nickel concentrations in persons with occupational exposures to nickel, provide the first demonstration that nickel concentrations in thyroid and adrenal glands are approximately equal to those in lung and are higher than in other organs, and suggest that biliary excretion may be a significant route for the elimination of nickel in humans.